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中国物理学会期刊

1—100 eV能区169Tm中子全截面测量与共振参数分析

CSTR: 32037.14.aps.75.20251263

Measurement of neutron total cross sections and resonance parameters analysis of 169Tm in the region from 1 eV to 100 eV

CSTR: 32037.14.aps.75.20251263
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  • 中子全截面不仅是核反应理论研究的重要参数, 也是共振参数提取和核数据库评价所必须的关键数据. 然而, 在低能共振区, 由于实验本底、样品自屏蔽效应和仪器展宽的影响, 不同实验的测量结果存在数据分歧. 本研究在中国散裂中子源反角白光中子束线(CSNS Back-n)上开展了169Tm的中子全截面测量, 采用翼形锂玻璃探测器对0.5 mm和4.5 mm厚度样品进行透射实验, 并结合锂玻璃闪烁体与饱和共振吸收技术, 定量评估并扣除了束内伽马本底, 获得了1—100 eV 能区的中子透射率和全截面数据, 结果与实验数据库符合较好. 结合在Back-n获得的中子俘获实验数据, 利用SAMMY程序对透射率进行了R矩阵拟合, 提取了该能区的共振参数, 初步验证了Knapová等观测到的8.037 eV处的新共振峰. 基于提取的参数, 采用Reich-Moore近似重构了169Tm中子全截面, 结果与ENDF/B-VIII.1 共振参数重构的截面符合较好, 为核数据库提供了新的参考. 本文数据集可在https://www.doi.org/10.57760/Sciencedb.j00213.00192中访问获取.

     

    The neutron total cross section is one of the most fundamental nuclear data. In the low-energy resonance region, discrepancies among measurements arise from experimental backgrounds, sample self-shielding, and instrumental broadening, which complicate the precise determination of cross sections. In this work, the neutron total cross section of 169Tm is measured at the Back-n facility of the China Spallation Neutron Source (CSNS). Wing-shaped lithium glass detectors are used to record the transmitted neutron signals from samples with thicknesses of 0.5 mm and 4.5 mm. The raw data are processed, including time-of-flight correction and normalization to the incident proton number, to account for the fluctuations in the proton beam intensity. The in-beam γ background is quantified using the saturated resonance absorption technique with glass scintillators. After background subtraction, transmission and total cross-section data are obtained in an energy range of 1–100 eV. The measured spectra are analyzed using the SAMMY code within the framework of the R-matrix. Neutron capture yield data are incorporated to improve the reliability of the extracted resonance parameters. For the resonance near 8 eV, the Γγ is set to the library average value of 86 meV. The resonance energy is determined to be 8.037 eV, consistent with the recently reported resonance by I. Knapová et al. and the neutron widths for both total spin states are evaluated. Based on the extracted parameters, the neutron total cross section of 169Tm is reconstructed using the Reich–Moore approximation. The reconstructed cross section shows good agreement with those recommended by ENDF/B-VIII.1 library, confirming the reliability of the resonance parameters extracted from the capture-transmission measurements. Overall, the present measurements and analysis provide a set of resonance parameters for 169Tm, enhancing the experimental foundation for both nuclear physics research and nuclear industry.
    The datasets presented in this paper, including the neutron transmission, neutron total cross section, and resonance parameters are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00192.

     

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